Re: find position in a list made by string by searching incomplete

*To*: mathgroup at smc.vnet.net*Subject*: [mg130372] Re: find position in a list made by string by searching incomplete*From*: Alexei Boulbitch <Alexei.Boulbitch at iee.lu>*Date*: Sat, 6 Apr 2013 05:09:30 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-newout@smc.vnet.net*Delivered-to*: mathgroup-newsend@smc.vnet.net

I have a list of strings like list1={{"a", "b something", "a", "a", "b", "c", "b"} In this list, 'something' is a sting that I will not know in advanced and there are several spaces between the 'b' and the 'something' in one string. The number of the spaces is unknown. I want to find out the position of the this "b something" sting in the list. So, I did, Position[list1, "b*"] and I also tried, Position[list1,"b"~~___ ] both of them gave me {} as results. Also Cases[list1,"b"~~___] or Cases[list1, "b*"] does not work. I can get the correct position only if I give the exact "b something" as the searching pattern. What is the easiest way to search with a incomplete string pattern in this case? Thanks for your help. Hi, It will go easily, if you transform the list of strings (or characters) into the list of symbols: list1 = {"a", "b something", "a", "a", "b", "c", "b"} {"a", "b something", "a", "a", "b", "c", "b"} list2 = Map[ToExpression, list1] {a, b something, a, a, b, c, b} Now, one can do it by several ways. For instance, this: Position[list2, (b a_)] {{2}} One can use the fact that the special form of "b something" gives it a Head that differs from that of all other terms. Indeed, Head /@ list2 {Symbol, Times, Symbol, Symbol, Symbol, Symbol, Symbol} this item has the head Times, while the others - Symbol. We can, therefore, do the following: Position[list2, Select[list2, Head[#] == Times &][[1]]] {{2}} or otherwise Position[Head /@ list2, Times] {{2}} I guess that one can see also few other ways. Have fun, Alexei Alexei BOULBITCH, Dr., habil. IEE S.A. ZAE Weiergewan, 11, rue Edmond Reuter, L-5326 Contern, LUXEMBOURG Office phone : +352-2454-2566 Office fax: +352-2454-3566 mobile phone: +49 151 52 40 66 44 e-mail: alexei.boulbitch at iee.lu